Fix: Remove default value for --verbose flag

This actually caused an error.

When executing `imag ids --verbose trace` for example, the `imag` binary
got the default value (as in `--verbose info`) supplied from clap. So
far, so good. Problem is that the implementation then forwarded that
flag to `imag-ids`, which resulted in the `--verbose` flag to be passed
_two times_ to `imag-ids`.

Somehow this is really strange, but it does not really matter. First of
all: A default of "Info" is still too high IMO. Default should be
warnings and errors, but no information printed. We like silent tools,
don't we?

Second is that the commandline argument forwarding mechanism of `imag`
is broken and this was a fix which helped debugging of the brokenness,
so this is acutally a step forward in this regard as well.

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

lib/core/libimagrt/src/runtime.rs

@@ -178,7 +178,6 @@ impl<'a> Runtime<'a> {
                 .required(false)
                 .takes_value(true)
                 .possible_values(&["trace", "debug", "info", "warn", "error"])
-                .default_value("info")
                 .value_name("LOGLEVEL"))
 
             .arg(Arg::with_name(Runtime::arg_debugging_name())